Lubricating oils

ABSTRACT

LUBRICATING OIL COMPOSITIONS COMPRISING CERTAIN SYNTHETHIC ALKARYL HYDROCARBON LUBRICANTS AND MINERAL LUBRICATING OILS HAVE IMPROVED PROPERTIES, SUCH AS OXIDATION STABILITY AND POUR POINT. A TYPICAL SYNTHETIC ALKARYL HYDOCARBON LUBRICANT CONTAINS FROM 61 TO 92 WEIGHT PERCENT DI-N-ALKYLBENZENES AND 5 TO 30 WEIGHT PERCENT TRIALKYL-SUBSTITUTED TETRAHYDRONAPHTHALENES. BECAUSE OF THEIR LOW POUR POINTS, THE LUBRICANTS OIL COMPOSITIONS ARE USEFUL IN CERTAIN SPECIFIC LOW TEMPERATURE (I.E., ARCTIC) OPERATIONS. IN ADDITION, THE LUBRICATING OIL COMPOSITIONS ARE USEFUL IN PREPARING LUBRICATING GREASES FOR LOW TEMPERATURE OPERATIONS.

United States Patent Office 3,812,035 Ratented May 21, 1974 3,812,035 LUBRICATING OILS Robert A. Krenowicz and William P. Scott, Ponca City, Okla., assignors to Continental Oil Company, Ponca City, Okla. No Drawing. Filed May 17, 1972, Ser. No. 254,015

Int. Cl. C10m 1/16' U.S. Cl. 252-59 4 Claims ABSTRACT OF THE DISCLOSURE Lubricating oil compositions comprising certain synthetic alkaryl hydrocarbon lubricants and mineral lubricating oils have improved properties, such as oxidation stability and pour point. A typical synthetic alkaryl hydrocarbon lubricant contains from 61 to 92 weight percent d-i-n-alkylbenzenes and 5 to 30 weight percent trialkyl-substituted tetrahydronaphthalenes. Because of their low pour points, the lubricating oil compositions are useful in certain specific low temperature (i.e., Arctic) operations. In addition, the lubricating oil compositions are useful in preparing lubricating greases for low temperature operations.

CROSS-REFERENCE TO RELATED APPLICATIONS Commonly assigned application Ser. No. 254,021, filed the same date as the present application, wherein the inventor is William P. Scott, discloses and claims a grease composition which comprises (a) a lubricating oil composition which comprises a blend of synthetic alkaryl lubricant and a synergistic amount of a mineral lubricating oil and (b) a grease-forming amount of a conventional grease-forming agent.

BACKGROUND Various petroleum fractions have been used as lubricants for many years. While the petroleum-derived lubricants (generally referred to as mineral lubricating oils) have been satisfactory for most uses, there are fields of use, as for example, jet engine lubricants and arctic oils, wherein the requirements render the conventional petroleum-derived lubricants either unsatisfactory or of marginal utility. In an attempt to solve this problem synthetic lubricants (for example, diesters) have been developed having improved properties, particularly improved viscosity and pour point properties. Unfortunately, however, many of the synthetic lubricants (e.g., diesters) have been relatively expensive. Moreover, while the diesters have been satisfactory as jet engine lubricants they have not been satisfactory as crankcase lubricants due to inferior oxidation stability and their corrosion of copper-lead bearings as a result of partial hydrolysis. For these reasons the diesters have not been used as low-temperature crankcase lubricants.

Synthetic alkaryl hydrocarbon lubricants have been developed which have superior physical properties to the mineral lubricants. U.S. Pats. Nos. 3,288,716 and 3,173,- 965 teach synthetic alkaryl hydrocarbon lubricants. While these materials are lower in cost than the diester-type lubricants, they are more expensive than the mineral lubricants. In addition, in some aspects the oxidation stability of these materials is inferior to the mineral lubricants.

We have discovered that mixtures of synthetic alkaryl hydrocarbon lubricants and mineral lubricating oils have certain improved properties (e.g., oxidation stability and pour point) over that of either lubricant alone. In other words, the mixtures produce a synergistic effect.

PRIOR ART To our knowledge there are no teachings that mixtures of synthetic alkaryl hydrocarbon lubricants and mineral lubricating oils produce a synergistic effect.

There are, however, several references which teach that synthetic alkaryl hydrocarbons, or compositions containing synthetic alkaryl hydrocarbons, have properties which render them particularly useful as lubricants. The following patents are representative of these teachings: U.S. 3,288,716; U.S. 3,173,965 and U.S. 3,544,472; Moreover, U.S. application Ser. No. 53,352, filed July 6, 1970, which will issue as Pat. No. 3,662,012 on May 9, 1972, teaches a process for preparing such a composition.

In addition, it is known that blends can be prepared of synthetic hydrocarbon lubricants and mineral lubricating oils. For example, British Pat. No. 1,144,615 contains such teachings. However, to our knowledge, there is no teaching that blends containing specific proportions of the two materials have a synergistic effect.

BRIEF SUMMARY OF THE INVENTION Broadly stated, our invention is directed to a lubricating oil composition comprising certain synthetic alkaryl hydrocarbon lubricants, as defined hereinafter, and a synergistic amount, in the range of about 11 to about 100 parts per 100 parts of synthetic alkaryl hydrocarbon lubricant, of a mineral lubricating oil.

In one aspect, our invention is directed to a method of improving one or more properties of a syntheticalkaryl hydrocarbon lubricating oil by the addition thereto of a synergistic amount, in the range of about 11 to about 100 parts per 100 parts of synthetic alkaryl hydrocarbon lubricant, of a mineral lubricating oil.

DETAILED DESCRIPTION Definition of synergistic amount The term synergistic amount, as used herein and in the claims, refers to that amount of the mineral lubricating oil which when added to the synthetic alkaryl hydrocarbon lubricant produces an improvement in one or more properties of the final composition, as compared to that obtained on one of the materials alone. For example, a composition comprising synthetic alkaryl hydrocarbon lubricant and 25% pale oil has better oxidation stability properties than does either the synthetic hydrocarbon lubricant or the pale oil. In this instance, the synergistic amount of pale oil is 33.3 parts per parts of synthetic hydrocarbon lubricant.

The synergistic amount varies according to the materials used and to the property being evaluated.

We have found that addition of various mineral oils to the synthetic alkaryl hydrocarbon lubricant produces a synergistic effect in at least the following properties: oxidation stability and pour point improvement (i.e., lowering of pour point).

Synthetic hydrocarbon alkaryl lubricant The synthetic hydrocarbon alkaryl lubricant used in our invention is characterized as containing a major amount 3 of di-n-long-chain alkaryls and a minor, but significant, amount of trialkyl-substituted tetrahydronaphthalenes.

In the di-n-long-chain alkaryls the long chain alkyl groups contain from about 6 to about 18 carbon atoms, more suitably from about 10 to about carbon atoms and preferably from about 11 to about 14 carbon atoms. The aryl moiety is phenyl, tolyl, or xylyl, but preferably is phenyl. Thus, the preferred di-n-long-chain alkaryls are di-n-alkylbenzenes wherein the alkyl groups conform to the long-chain alkyl definition of the foregoing. The term n-alkylbenzenes as used herein refers to benzenes containing a substantially straight-chain alkyl group, wherein, preferably, at least 95 percent of the alkyl substituents are bonded to the benzene nucleus through a secondary carbon atom of the respective alkyl group. While we prefer the term n-alkylbenzenes other terms such as linear alkylbenzenes or straight-chain alkylbenzenes are equally descriptive.

The trialkyl-substituted tetrahydronaphthalenes can be represented by the formula H Rawherein R and R contain from 1 to about 13 carbon atoms each, with the sum of R and R being from about 6 to about 14 and R and R contain from 1 to about 16 carbon atoms with the sum of R and R being from about 9 to about 17. The alkyl groups, R R R and R are straight-chain.

The trialkyl-substituted tetrahydronaphthalenes have the same boiling range as the di-n-alkylbenzenes. In addition, they have approximately the same molecular weight.

In addition to the di-n-long-chain alkaryls and trialkylsubstituted tetrahydronaphthalenes the synthetic hydrocarbon alkaryl lubricant can contain minor amounts of miscellaneous alkyl aromatic compounds.

The synthetic hydrocarbon alkaryl lubricant composi tion has the following composition:

Component: Percent by weight Di-n-long-chain alkaryls 61-92 Trialkyl-substituted tetrahydronaphthalenes 530 Miscellaneous alkyl aromatics: less than 15.

Preferably: less than 10.

The materials are also characterized as having the following properties:

Viscosity index 80 to 116 Pour point, F. 40 to -80 Molecular weight range 350 to 526 Preferably 375 to 480 The synthetic hydrocarbon alkaryl lubricants can be prepared by any of several methods. They can be prepared by alkylating benzene and tetrahydronaphthalene and blending the resulting product. Also, they can be prepared by alkylating a mixture of mono-n-alkylbenzenes and dialkyl-substituted tetrahydronaphthalenes with a suitable alkylating agent. A particularly suitable method of preparing the synthetic hydrocarbon alkaryl lubricants is by the disproportionation of a mono-n-alkylbenzenerich feedstock using HF-BF aluminum bromide or aluminum chloride as the catalyst.

While we are describing in detail the disproportionation method of preparing the synthetic hydrocarbon lubricant, it is to be understood that any composition having the compositions and physical properties described in the foregoing is suitable for use in our invention.

Suitable mono-u-alkylbenzenes are those containing from about 6 to about 18 carbon atoms in the alkyl groups. Preferably, the alkyl groups of the mono-n-alkylbenzenes contain from about 10 to about 15 carbon atoms. The term n-alkylbenzenes" has been defined in the foregoing.

Suitable mono-n-alkylbenzenes are those containing from about 6 to about 18 carbon atoms in the alkyl groups. Preferably, the alkyl groups of the mono-n-alkylbenzenes contain from about 10 to about 15 carbon atoms. The term n-alkylbenzenes has been defined in the foregoing.

A particularly suitable material for use in preparing the disproportionated product is a composition, containing a substantial amount of mono-n-alkylbenzenes conforming to the foregoing description, produced in accordance with the process of U.S. Pat. No. 3,316,294. Briefly, U.S. 3,316,294 relates to a process of preparing a detergent alkylate, wherein the process comprises the following steps, broadly stated: (a) separating a fraction of substantially straight-chain C -C hydrocarbons from a petroleum distillate substantially free of olefins and containing said straight-chain hydrocarbons together with non-straight chain hydrocarbons, (b) chlorinating said fraction to the extent whereby between about 10 and about 35 mole percent of the straight-chain hydrocarbons present are substantially only mono-chlorinated, (c) alkylating an aromatic compound, eg benzene, with the chlorination product of step (b) in the presence of an alkylation catalyst, and (d) recovering from the reaction mass, by distillation, a fraction consisting essentially of mono-nalkvlbenzenes.

While U.S. 3,316,294 concerns a process which can use C to C hydrocarbons the present invention uses hydrocarbons which can contain from about 6 to about 18 carbon atoms. The C -C hydrocarbons can be obtained by a modification of the process described as step (a) of U.S. 3,316,294. In addition, other means of obtaining a C -C hydrocarbon fraction will be apparent to those skilled in this art. When it is desired to use an alkylbenzene containing 10 to 15 carbon atoms in the alkyl group, this selection can be made either in the initial feedstock or by fractionation of the alkylbenzene product.

Process conditions for disproportionation reaction Preferably, the disproportionation reaction is conducted using aluminum chloride as the catalyst. The amount of the catalyst which is used can vary from about 0.1 weight percent to about 10 Weight percent based on the mono-n-alkylbenzene starting material. Preferably, the amount of catalyst is from about 0.5 weight percent to about 5 weight percent.

In some cases it is desirable to use a proton-donor promoter with the aluminum chloride catalyst. Suitable promoters include any material which, when added to the catalyst, yields a proton. Preferred promoters are hydrogen chloride and water. The amount of promoter is typically about 4 weight percent based on the weight of the catalyst employed. It should be emphasized that anyone skilled in this art can readily determine the necessity of using a promoter and the amount of promoter, if used.

The disproportionation process, suitably, is conducted at a temperature of from about 20 C. to about 130 C. Since maximum yields of the di-n-alkylbenzenes are obtained at temperatures between about 65 C. and C these temperatures are preferred.

Following the reaction, the reaction mass is distilled in order to remove the benzene, paraflins and unreacted mono-n-alkylbenzenes. The desired product is the disproportionated material distilling in the range of about 165 C. to about 300 C. at 5 mm. Hg. This material has an average molecular weight in the range of about 350 to about 470. In conducting the distillation, more suitably the lower cut point is 185 C. at 5 mm. Hg. Preferably, the lower cut point is 197 C. at 5 mm. Hg.

In some instances the desired fraction is obtained by distilling from the disproportionated product a select fraction or overhead amounting to from about to about 90 percent of the disproportionate.

The term mineral lubricating oil, as is well known, refers to materials resulting from the refining of crude petroleum. Particularly suitable mineral lubricating oils are the following: pale oils, naphthenic oils, and bright stocks. While we believe the terms pale oil, naphthenic oils and bright stocks to be well-known to those skilled in this art in order to render our disclosure more complete a brief discussion will be provided concerning these materials.

In the refining of petroleum the crude petroleum is subjected to a distillation which produce straight-run gasoline, kerosine, and gas oil. The residue of reduced crude is used to prepare the lubricating oil. Both naphthenic and pale oil are the distillate fraction Whereas bright stock is the bottom fraction. Conventionally, the pale oils and bright stocks are subjected to further treatment to improve color and reduce the wax content thereof.

While both pale oils and naphthenic oils are distillate oils, they differ in many respects such as type of crude petroleum from which they are derived, chemical composition and physical properties. Naphthenic oils have a greater amount of aromatics, lower viscosity indexes, and lower pour points than do the pale oils. Anyone skilled in this art can distinguish pale oils and naphthenic oils on the basis of the following properties: viscosity index and pour pont.

As is generally described in the foregoing, the term bright stock refers to a higher-viscosity, solvent-refined, dewaxed lubricating oil derived from a paraffinic crude oil.

The naphthenic oils are preferred in our invention since they provide a synergistic effect in more instances. Particularly, with regard to pour point effect in lubricating oil blends, the naphthenic oils are more effective over a wider composition range.

In order to make our disclosure of suitable mineral lubricating oils more complete the following book is made a part of our disclosure: Petroleum-Prehistoric to Petrochemicals"; G. A. Purdy; Copp Clark Publishing Company, Vancouver, Toronto, Montreal, Canada (1958). The following pages thereof are especially pertinent: 225, 226, 227, 228, 231, 234, 224 and 373.

Description of synergistic amounts Having defined the term synergistic amounts and having described the nature of the materials used in our invention, the following table is provided to illustrate the preferred range for synergistic amount for various prop erties and various mineral lubricating oils.

Lubricating oil composition 1 Parts per 100 parts, synthetic hydrocarbon lubricant.

Uses for our invention As stated previously herein, the lubricating oil compositions of our invention are particularly suitable for preparing grease compositions for low temperature use.

While the lubricating oil compositions of our invention exhibit a synergistic effect in several properties, it should be noted that some properties (particularly viscosity index) of the composition are not improved. In fact, some properties (particularly viscosity index) are intermediate between that for the synthetic alkaryl hydrocarbon lubricant and the mineral lubricating oil. From the data shown in the tables, however, it will be apparent that many of the compositions coming within the scope of our invention, while having a lower viscosity index than that of the synthetic alkaryl hydrocarbon lubricant alone, still have a relatively good viscosity index.

In addition to being useful for preparing low temperature greases the lubricants of our invention are also useful for other purposes, such as crankcase lubricants and hydraulic fiuids.

In order to disclose the nature of the present invention still more clearly, the following examples, both illustrative and comparative, will be given. It is to be understood, however, that the invention is not to be limited to the specific conditions or details set forth in these examples except insofar as such limitations are specified in the appended claims.

MATERIALS USED IN EXAMPLES Synthetic hydrocarbon alkaryl lubricant The synthetic hydrocarbon alkaryl lubricant was prepared by disproportionation of a mono-n-alkylbenzene fraction prepared in accordance with the process of US. Pat. No. 3,316,294 as described hereinbefore. The monon-alkylbenzene contained predominantly C alkyl groups. The product had the following composition:

Volume percent Di-n-alkylbenzenes n 69.3 Trialkyl-substituted tetrahy-dronaphthalenes 22.3 Naphthalene 3.6 Indenes 2.9

Diphenylalkanes 1.6 Miscellaneous compounds 0.3

The components of the composition were in a molecular 1 Hydrogenated.

7 8 Pale oils and bright stock TABLE I-C ntimmd The pale oils and bright stock had the following propggggg gg 2 ,1 1 :3 erties: lube 8 pale oil index F.

5 Naphthenie Viscosity, cs. at Pputr oil E Olll 100 F. 210 F. v.1. p F. 110 --00 4o -20 so pale oil 15. 60 a. 23 95 +5 9 6 100 pale oil 21. 7 4. 2 96 0 Bright stock 575 33 96 +10 10 110 fi0 EXAMPLE 1 a It? Blends were prepared containing various amounts of r, gig g the synthetic hydrocarbon lubricants, the naphthenic lubrieating oils and the pale oils. The pour point properties :2 :gg and viscosity indexes of the blends, together with that 105 -c5 of 100% of the oils used in the blends, are shown in 88 :2? Table I.

110 60 TABLE I lComposltlon, wt. percent 011 blend] 103 60 lsiyrtbhetieJ Vits- Pputr 96 45 I008 011 (051 0111 liibe r 80 pale oil inder r p Hydrogenated -co +5 :28 30 EXAMPLE 2 -30 This example illustrates the effect on oxidation stability by blending 100 pale oil, naphthenic oil A or bright stock with the synthetic hydrocarbon lubricant. The test used was Federal Test Method Standard No. 791-13, Test Method No. 5308.6, as of Jan. 15, 1969, :32 with the following exception: no metal catalyst was employed. (Inasmuch as this test method is quite lengthy, :3 is published, and well recognized, it will not be described gg herein.) The following compositions were tested:

100% Synthetic Hydrocarbon Lubricant 100% 100 Pale Oil 100% Naphthenic Oil A 75% Synthetic Hydrocarbon Lubricant 25% 100 Pale Oil 75 Synthetic Hydrocarbon Lubricant 25 Naphthenic Oil A :gg 50% Synthetic Hydrocarbon Lubricant 50 50% Naphthenic Oil A g g Synthetic Hydrocarbon Lubricant 25% Bright Stock 166 :38 50% Synthetic Hydrocarbon Lubricant 40 84' -7s 50% Bright Stock The results of the tests are shown in Table H.

TABLE II Oxidation stability, 72 hours at 347 F.

Fluid change Tube deposit rating Oil composition Bottom 100% synthetic hydrocarbon lubricant Trace None. 100% 100 pale oils- 13. 9 Heavy carbon. 100% uapththenic 011A 62. 5 2. 5 -.do Do. 75% synthetic hydrocarbon lubricant, 25% 100 pale o 5. 5 1.1 Light None. 75% synthetic hydrocarbon lubricant, 25% naphthenico 9.9 1.0 ..do Medium 50% synthetic hydrocarbon lubricant, 60% 100 pale oil 5. 4 1. 2 do-. None. 50% synthetichydrocarbonlubricant}50%naphthenic oilA- 19.0 1.3 .do Heavy. 76% synthetic hydrocarbon lubricant, 25% bright stock-. 6. 1 0. 6 None. None. 50% synthetic hydrocarbon lubricant 5.4 0. 7 do Do.

1 A different, but substantially identical, product to that described.

Thus, having described the invention in detail, it Will be understood by those skilled in the art that certain variations and modifications may be made without departing from the spirit and scope of the invention as defined herein and in the appended claims.

We claim:

1. A lubricating oil composition comprising a synthetic alkaryl hydrocarbon lubricant and a synergistic amount, in the range of about 11 to about 100 parts per 100 parts of synthetic alkaryl hydrocarbon lubricant, of a naphthenic mineral lubricating oil, said synthetic hydrocarbon lubricant containing from about 61 to about 92 percent by weight di-n-alkylbenzenes wherein the alkyl group contains from about '6 to about 18 carbon atoms and from about 5 to about 30 percent by weight trialkyl-substituted tetrahydronaphthalenes, said synthetic hydrocarbon alkaryl lubricant having the following physical properties:

viscosity index: 80 to 116 pour point, 0 F.: 40 to -80 molecular weight range: about 350 to about 526 2. The lubricating oil composition of claim 1 wherein the alkyl groups of said di-n-alkylbenzenes contain from about 10 to about 15 carbon atoms.

3. The lubricating oil composition of claim 2 wherein the alkyl groups of said di-n-alkylbenzenes contain from about 11 to about 14 carbon atoms.

4. The lubricating oil composition of claim 3 wherein the synthetic alkaryl hydrocarbon lubricant has a molecular weight in the range of about 375 to about 480.

References Cited UNITED STATES PATENTS 3,544,472 12/1970 Bray et a1 252-59 1,815,022 7/1931 Davis 25259 X OTHER REFERENCES Berry et al., Preprint Am. Chem. Soc., div. of Petroleum Chem. (1956), pp. 70-76.

Kirk-Othmer, Encycl. of Chem. TechnoL, vol. 8

WILLIAM H. CANNON, Primary Examiner 

